Despite decades of basic and clinical research, breast cancer remains one of the most deadly non-communicable diseases affecting principally women, although men are also diagnosed with this disease. According to the GLOBOCAN Project of the World Health Organization's International Agency for Research on Cancer, it was estimated that in 2008 the incidence of breast cancer nearly 1.4 million and that in the same year more than 450 thousand women were killed by the disease. While much has been learned recently regarding how breast cancer works at the molecular level, clinicians still rely on therapeutic modalities such as surgery, radiation, hormone therapy and chemotherapy that would have been familiar to oncologists of a generation ago. Early diagnosis, made possible by advances in imaging technology and molecular diagnostics, factors greatly in the success of any treatment. Although the efficacy of all these treatments has improved over the years, the improvement in cure rates and the increase in longevity have been incremental. Even the new targeted therapies resulting from the revolution in molecular oncology have, for the most part, improved outcomes only modestly. For example, Herceptin®, which targets the HER2 receptor, is effective only for the 20-25% of women having breast cancer whose tumors are HER2 positive.
Two of the most challenging aspects of managing breast cancer patients are metastasis and recurrence.
Metastasis occurs when the breast cancer spreads to distant organs from the primary tumor. While it is often possible to resect the primary tumor, it is the metastases that frequently end up killing the patient because they become too numerous or entwined with healthy host tissue to treat surgically. According to the American Cancer Society, the five year survival rate in the United States for patients first diagnosed with Stage IIIB breast cancer in 2001 and 2002 was 41%, which dropped to only 15% at Stage IV (i.e., metastatic breast cancer).
Recurrence is the phenomenon by which breast cancer returns after initially responding to treatment and apparently disappearing. Apart from the emotional toll inflicted on patients and their families, recurrence is problematic because the returning cancer may be less responsive to the therapy or therapies that were effective to fight the first cancer. For other patients, prior treatments for the first cancer may have caused irreversible side effects, such as cardiac or neurological damage. In such patients, the risks of using the same therapy to fight the recurrent cancer may be too great. Under these circumstances, a patient may have fewer treatment options with a concomitantly greater risk of mortality.
While improvements in surgery, radiation treatment, hormonal therapy, chemotherapy and the advent of targeted therapies have increased the longevity of patients stricken by breast cancer, many such patients continue to die within months to a few years after their diagnosis. An urgent need therefore exists for new treatments effective against breast cancer and its recurrence.